dopant atoms evaporating from semiconductor surface region during high temperature treatments can be reintroduced into semiconductor causing undesired variations in dopant concentration at the surface; highly undesired effect; of particular concnern in high-temperature epitaxial deposition processes.

epitaxy

process by which thin layer of single-crystal material is deposited on single-crystal substrate; epitaxial growth occurs in such way that the crystallographic structure of the substrate is reproduced in the growing material; also crystalline defects of the substrate are reproduced in the growing material.

outdiffusion

undesired effect occurring at high temperature: dopant atoms diffuse from the material featuring high doping level to the material featuring low doping level; common in high temperature epitaxial deposition where it prevents sharp change in dopant concentration between epi layer and the substrate; temperature of epitaxial deposition must be reduce to control outdiffusion.